To evaluate the application of the lower tear meniscus parameters measured by anterior segment optical coherence tomography (AS-OCT) in dry eye diagnosis.
A prospective randomized clinical controlled study was conducted.One hundred and thirteen dry eye patients (226 eyes) and 206 healthy volunteers (410 eyes) were enrolled from May 2015 to October 2016 in Shanxi Eye Hospital.The lower tear meniscus height (LTMH), lower tear meniscus area (LTMA), lower tear meniscus depth (LTMD), the corneal epithelial thickness (CET) at central 6 mm and the corneal thickness at central 6 mm were measured by RTVue-XR.The measurement results of the two groups were compared and the ROC curve was drawn.The dry eye group and the control group were divided into four age groups: >20-30 years old, >30-40 years old, >40-50 years old and >50-60 years old.The changes of the parameters of the tear crescent in different age groups were compared.The changes of the lower tear meniscus with age were analyzed by linear regression equation.This study was approved by the Ethics Committee of Shanxi Eye Hospital.All operations were performed in accordance with the Helsinki Declaration, and written informed consent was obtained from each subject prior to any medical examination.
The values of LTMH, LTMD and LTMA in dry eye group were (216.08±67.26)μm, (116.50±29.13)μm, (0.012 9±0.006 7)mm2, respectively, which were lower than (333.71±50.38)μm, (139.56±28.76)μm, (0.026 6±0.007 4)mm2 in control group, with statistical significance between the two groups (all at P<0.05). The CET values of each quadrant in the central area of 2 mm, 2-5 mm and 5-6 mm in the dry eye group were significantly lower than those in the control group, with statistically significant differences between the two groups (all at P<0.05). The corneal thickness of central 5-6 mm region, 1/8 above the superior nasal quadrant in the central range of 2-5 mm and 1/8 above the superior quadrant was not statistically significant between the two group (all at P>0.05); the corneal thickness values of the other quadrant in dry eye groups were lower than those in control group, the differences were statistically significant (all at P<0.05). The cut-off values of LTMH, LTMD, LTMA, CET at central 2 mm and corneal thickness at central 2 mm were 269.83 μm, 122.02 μm, 0.023 2 mm2, 54.16 μm, 531.50 μm, respectively, the sensitivity were 85.4%, 88.9% 96.5%, 77.0%, 66.8%, respectively; the specificity were 91.7%, 70.5%, 75.1%, 56.8%, 59.8%, respectively.The values of LTMA, LTMH and LTMD in each age group of dry eye group were significantly lower than those of the control group (all at P<0.05). Linear regression analysis showed that LTMH was decreased by 3.966 μm and LTMD was decreased by 2.381 μm along with the increase of 1 year age in the control group, while LTMH was decreased by 1.293 μm along with the increase of 1 year age in the dry eye group.Compared with the control group, the area of the lower tear crescent image in the dry eye group was reduced, the boundary line was blurred and the coherence was poor in varying degrees, and the turbidity of the tear was increased.
AS-OCT can objectively reflect the shape of the lower tear meniscus parameters, central CET and central corneal thickness changes.The LTMH and LTMD of normal people are decreased with the increase of age.LTMA and LTMH have high diagnostic efficacy for dry eye and are expected to become one of the important methods for dry eye screening.